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particle of fluid about 9 and 1830 years to travel 10 meters <br /> on-- and offsite, respectively. For the worst case scenario, <br /> it would take a fluid particle 4 years to travel 10 meters <br /> (32.8 feet) . <br /> Di5puS�dOn Qf Results <br /> The previous analysis and calculations were based on the <br /> assumption that the porous media is isotropic and <br /> homogeneous. These conditions, however, seldom exist in the <br /> natural subsurface environment. The aquifer located beneath <br /> the site is neither isotropic nor homogeneous. It exhibits <br /> M• variations in physical properties both vertically and <br /> horizontally. Therefore, the hydraulic conductivity <br /> ' determined by the slug test should only be considered <br /> accurate within an order of magnitude of actual values at the <br /> f specific point within the porous media. Based on the average <br /> calculated hydraulic conductivity test value of 0.015 meters <br /> per day, the actual hydraulic conductivity could range from <br /> 0.0015 to 0.15 meters per day. According to Bouwer (1978) , <br /> this range of hydraulic conductivity values is typical for <br /> surface clay soils which is consistent with the clay to silty <br /> clay soils encountered at the site. <br /> The pump test results reflect the aquifer parameters over an <br /> effective radial distance beyond which no head difference <br /> will be dissipated. The effective radial distance ,for this <br /> t aquifer under the present conditions was calculated to be <br /> approximately 71 feet using the Bouwer and Rice (Bouwer, <br /> i 1978) equation. The hydraulic conductivity value determined <br /> for this site based on the pump test is higher than the value <br /> calculated from the slug test data. This may be due to the <br /> i location of the pumped well, MW-3, which is near the edge of <br /> the gravel backfill of the underground storage tanks. The <br /> predicted hydraulic conductivity value from the pump test is <br /> typical for fine to medium sand units, whereby the <br /> calculation method provides an average value of the hydraulic <br /> conductivity over the effective radius distance. <br /> It should be noted that the contaminant movement does not <br /> necessarily occur at the same rate as ground water movement. <br /> Darcy's law does not consider the hydrodynamic processes of <br /> advection and dispersion that are involved in the transport <br /> of contaminants in ground water. <br /> lY <br />